5-Hydroxymethylfurfural (5-HMF) has gained interest as bio-based building block. However, the road to the commercial production of 5-HMF has been paved with difficulties due to its instability under both acidic and basic conditions, and its sensitivity to Cannizaro reaction, oxidation and polymerization.

C. Oliver Kappe, University of Graz, Austria, and colleagues prepared for the first time the potential new platform molecule H²MF in pure form and converted it to the polyester precursor 5-hydroxy-4-keto-pentenoic acid (HKPA).
The researchers performed singlet-oxygen oxidation of 5-HMF in continuous flow mode using rose Bengal as photosensitizer in an environmentally benign iPrOH/H₂O solvent mixture. The resulting butenolide (H²MF) was formed selectively in high yield. The procedure proved to be scalable and applicable to related bio-based furfurals.

Moreover, preliminary results show that H²MF is an interesting intermediate for the production of poly-HKPA, a novel biopolymer.

• Singlet-Oxygen Oxidation of 5-Hydroxymethylfurfural in Continuous Flow,
  Thomas S. A. Heugebaert, Christian V. Stevens, C. Oliver Kappe,
  ChemSusChem 2014.
  DOI: 10.1002/cssc.201403182